垂直中心扭曲算法

    private void updateMesh(float fraction) {
        float[] src = mOrig;
        float[] dst = mVerts;
        float startX = mMaxDistance * fraction;
        for (int i = 0; i < MESH_COUNT * 2; i += 2) {
            float sx = src[i];
            float sy = src[i + 1];
            if (sx > startX) {
                dst[i] = sx;
                dst[i + 1] = mHalfHeight;
            } else if (sx < startX - mRotateAreaWidth) {
                dst[i] = sx;
                dst[i + 1] = sy;
            } else {
                float input = (startX - sx) / mRotateAreaWidth;
                float toCenter = sy - mHalfHeight;
                dst[i] = sx - toCenter * FloatMath.cos(HALF_PI * input) * .35f;
                dst[i + 1] = mHalfHeight + toCenter * FloatMath.sin(HALF_PI * input);
            }
        }
    }